Margaret A.WinkerMD, Deputy EditorPhil B.FontanarosaMD, Interim Coeditor
To the Editor: In their meta-analysis, Dr Fleischmann and colleagues1 reported that exercise ECHO has better specificity and therefore higher overall discriminatory capability than exercise SPECT imaging. We believe these conclusions are flawed for several important reasons.
The reference standard in all of the studies included in the meta-analysis was a stenosis of 50% to 70% on coronary angiography. This criterion standard is widely recognized to be poorly reproducible with a high degree of interobserver and intraobserver variability.2 Studies have shown that assessment of coronary flow reserve by cardiac catheterization is a much more accurate criterion than is luminal diameter stenosis. Impaired coronary vasodilatory reserve corresponds to a reversible myocardial perfusion defect with a 93% predictive accuracy.3 In contrast, angiographically determined stenosis severity is only loosely related to coronary flow reserve, especially in stenoses in the range of 50% to 80%. Many "false" positives found by SPECT (when using angiography as the criterion standard) are "true" positives when assessed by coronary flow-reserve measurement.
O'Keefe, Jr JH, Bateman TM, Gibbons RJ. Exercise Echocardiography vs Exercise SPECT Testing. JAMA. 1999;282(17):1621-1622. doi:10.1001/jama.282.17.1621-JLT1103-2-2